regarding solid vs. stranded wire...
this is to add a some info to Lena's great post. it's been a while since i've read about these issues, but i'll do my best. This post is long, but please read carefully. i won't come down on either side, stranded or solid.
"the Skin Effect" is primary differentiating factor between solid, stranded, and even insulated and uninsulated wire. Everything else interacts with this issue. Strands, insulation, winding/twisting, even wire cross section (it' not ALWAYS made to be round).
At the heart of the skin effect is the physic involved in electrical conduction. electrical signal travels almost exclusively on the surface of a metal, not at it's core. This is true of stranded wires also since they are many small solid strands.
Take a solid core insulated wire. A signal travels along only the outer diameter of the wire. This wire can interact with the insulation/dielectric. The argument against solid core says that the dielectric material which shouldn't have any effect on the signal, does.
For a stranded wire, the surface area of the wire is increased dramatically as each strand has an intermediate diameter that sums to an overall outer diameter. In simple view, this ought to be good. But, while providing more surface area for the signal to travel, in addition to dielectric interaction, the solid core people would say that the signal from each strand can now interact with the other strands, and the properties of the bounded surfaces would act differently than the outer diameter. Please keep in mind there would both be gaps between the strands, and strands in direct contact with each other. (Can you see why the physics can become hairy?).
This is just the dielectric we're talking about.
Let's move on...more on the skin effect...
Even assuming you have two OFC wires, ignoring grain structure, even trace amounts of anything could affect the signal carrying ability of the wire. As I have mentioned before, the signal travels on the wire surface, and also, it quickly diminishes carrying capacity as you head toward the center of the solid or strand. But just because it diminishes, does not mean the signal diminishes at the same rate, without favoring certain frequencies. Basically, the source and refinement of the wire could/can make a difference. This is also takes part in the skin effect.
Finally, let's talk about wire geometry. Likely somewhere after the dawn of Radio Shack and zip cord, people have been devising various ways to form cable to try and improve the sound. For the longest time, cables sat in "voodoo" mystique, because cables weren't that developed, and it didn't matter when your 78's, and LP's were so prone to deviation (let's not talk about static, or phono pickups with moving coil vs. moving magnets!) So...back to the story. People have been trying (and trying...) different cable geometries to find "THE ANSWER". I remember seeing a few companies sell flat solid wire to increase surface area. I still see other companies using different gauge strands, and different winding, braiding, and even "twists per inch" to tweak out better sound. Long's the punch line.
There's good solid core, there's bad solid core. There's good stranded, there's bad stranded.
Even worse, based on your exact models used in your set-up (your components & speakers, and other wires), your cables interact with all these.
To sum all this, basically, better conductor, better insulation, and better geometry can improve your cable, but ultimately, it's how they work around the skin effect that creates any hopefully appreciable improvement in the sound.
Remember, this is all physics that is extremely difficult to the discerning ear experiences something beyond our capacity to empirically measure for the time being.
Ultimately, buy some cheap zip wire, (hey, it's cheap! help out radio shack!) use it. You'll always have spare cable in a pinch. Buy some better wire (it's not uncommon to test out wires from higher end stores which is a great reason to patronize brick & mortar), and while you're there, pick the brains of the salespeople (preferably a mid to hi-fi audio place that doesn't sell low or midgrade Monster Cable), tell them what kind of sound you like, what kind of music you listen to, what equipment you have, and what percentage of listening is audio or A/V, and bring home a set for listening.
With all the variables I've mentioned, along with all the companies who make cables (I cry to think about doing DIY wire), "it's a jungle" is an understatement. Just notice if you notice a difference, and measure if you think that it's worth the cost. Who knows... maybe you'll become a cable junkie! Either way, once you've figured out what works, the satisfaction will leave you grinning for quite a while. Happy shopping!